WASHINGTON - Four states - Texas, Florida, Georgia and Arizona - will gain two seats each in the U.S. House of Representatives as a result of the new population numbers released by the Census Bureau Thursday. The biggest losers are New York and Pennsylvania, each giving up two seats.

Nationally, the U.S. population reached 281,421,906 on census day last April 1, a gain of 13.2 percent. The population was larger than expected, probably because the census did a better-than-usual job of counting residents living in the country illegally, census director Kenneth Prewitt told a news conference.

Texas, the home state of President-elect George W. Bush, toppled New York as the second most populous state, with 20.9 million residents. It was the first time since the census of 1810 that New York was not ranked first or second. California remains the nation's most populous state with a record 33.9 million people and will pick up one new seat in the House.

While all 50 states gained in population during the 1990s, the District of Columbia declined. Its population fell to 572,059, down from 606,900. Nevada recorded the highest rate of population growth in the 1990s: 66 percent.

The shift in congressional seats demonstrated that the nation's population growth keeps moving toward the West and the South.

The West grew by 19.7 percent and the South by 17.3 percent. By contrast, the Northeast showed an anemic growth rate of 5.5 percent, while the Midwest population expanded by 7.9 percent.

For the West and South, the growth was steady during the last decade, without the large spikes in numbers recorded in previous census tallies. A decade ago, California picked up seven House seats, Florida four and Texas three.

The future presidential electoral map looks a little more favorable for the Republicans. States carried by President-elect George W. Bush picked up a net gain of seven seats, giving them seven more electoral votes.

The figures issued Thursday are the basic census numbers used to apportion 435 House seats among the states.

The Census Bureau is now studying a special supplemental population survey to decide whether to recommend adjusting the official census figures by a statistical sampling technique. The big political question for the new administration will be whether to approve adjusted figures as the basis for the states to redraw their House districts, and as the method to disburse about $200 billion a year in federal funds.

"We know that a census number is an estimate, it's not the truth," Prewitt said. "We try to get that estimate as close as we can to the truth." And that's why the sampling study is under way, he said.

Because the census traditionally is more likely to undercount members of minority groups, the political stakes are high. Democrats, with greater voting support among minorities, favor the adjusted figures. Republicans want to stick with the traditional head count.

In the House, now balanced on the razor's edge with Republicans holding essentially a five-seat majority, the new population figures are likely to cause a political shakeout in two years. The great unknown is whether the House's fresh tilt toward the South and West will strengthen the Republican majority or create new opportunities for Democratic gains.